Drug delivery devices (e.g., infusion devices or pumps) can experience conditions that can lead to under-delivery or over-delivery of an infusate into a patient. For example, blockages in a fluid path (e.g., as caused by an occlusion) can cause a backup of fluid within the pump and a subsequent increase in fluid path pressure. When a blockage clears, the pressurized infusate can be delivered in a single bolus in an undesirable or unintended manner.
When air is trapped in the fluid path, changes in atmospheric pressure can cause the trapped air to expand or compress and to displace (e.g., by suction) fluid into or out of the patient. These situations can also cause under-delivery or under-delivery of the infusate into the patient. Swimming or flying are examples of common activities engaged in by a patient that can result in under-delivery and over-delivery without the patient's knowledge.
Additionally, when air is trapped in the fluid path, changes in ambient temperature can also cause the trapped air to expand or compress and to displace fluid into or out of the patient. Similarly, these situations can also cause under-delivery or over-delivery of the infusate into the patient. Swimming in the ocean or swimming in an unheated pool or using a heated blanket are examples of common activities engaged in by a patient that can result in under-delivery and over-delivery of the infusate without a patient's knowledge.
Many conventional drug delivery devices including infusion devices or pumps detect occlusions by monitoring the time it takes for the pump to actuate. This conventional approach can produce erroneous results based on variabilities within the drive system (e.g., due to friction, power sagging, mechanical variability of parts, etc.).
Even conventional systems that directly measure the pressure within the pump fluid path often do not detect changes in atmospheric pressure which can lead to over-delivery and under-delivery. These conventional systems typically utilize pressure sensors which measure pressure relative to atmospheric pressure and are incapable of detecting any change in atmospheric pressure which can lead to over-delivery and under-delivery without a patient's knowledge as described above.
Accordingly, what is needed is a drug delivery device with improved capabilities for detecting under-delivery and over-delivery conditions during intended delivery periods or unintended delivery periods that can be caused by a variety of factors including changes in atmospheric pressure.